Sunday, December 30, 2012

Two points are completely out of phase if their motions are always opposite

Superwaves are created when two identical waves move toward each other

Path Length and Path difference

Path length: the distance from a point to the source of a wave

Path difference(Δ): the difference between the path lengths of two different waves

If two point sources vibrate in phase with each other, they would be in-phase at points where Δ is a whole number multiple of λ

Waves at Boundaries

The frequency of a wave never changes

Snell's law: n×sin(θ) is constant (n is the index of refraction)

If a wave travels from a faster medium to a slower medium, the transmitted wave becomes inverted

Interference from two point-sources

If a point P is very far away from the two sources, then Δ= d×sin(θ), where d is the separation between the sources, and θ is the angle between the perpendicular bisector of the sources and the line joining P and the midpoint of the two sources

Young's double slit experiment:

Problem: to have two point sources of light that are coherent

The first slit acted as a point source of light

The double slit acted as two point sources of light

On the screen, the bright fringes are where the antinodal lines are

The dark fringes are where the nodal lines are

Interference of thin films:

Use the theory of "waves at boundaries" and path difference to do these problems